Review r0 M3. The indirect sweep disposed stale resolutions without holding
their gates, and any reader/writer that fetched a handle before waiting on its
gate could then use an instance a sibling had evicted and disposed - a
spurious comms fault and Degraded. The sweep now evicts under each key's gate,
and read/write re-resolve the handle once the gate is held (reconnecting
single-flight if it was evicted; a retired state never reconnects).
Refs #738
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
16c2045cab